With rapid progress in biotechnology and medical treatment, the molecular biological detection has become a major subject of investigation. The molecular biological detection utilizes specific molecular markers or specific activity of specific molecules to distinguish different molecules by selective detection. The molecular biological detection, which is for sensing the presence of trace amount of protein, nucleic acid, or compounds in organism or environment such as early diagnoses of diseases and detection of environmental factors such as environmental hormones in high-specificity and high-sensitivity manners, is particularly important in different fields including medical science, life science, food detection, environmental sanitation, etc. The developing of high-sensitivity, instant, accurate, high-throughput detections has currently become a major trend of investigation.
It is therefore a challenging and interdiscipline-intergrated subject to develop a new detection technology by utilizing the existing maturated or developing technologies effectively. In recent years, there are disclosed many biosensors or sensing methods, which can be classified into sensing methods of labeling the target substances with fluorescence or luminescent markers and the high-sensitivity methods such as surface plasma resonance (SPR), Quartz crystal microbalance (QCM), carbon nanotube field-effect transistor (CNT FET) and nanowire FET for detecting the bonding to the target substances. The target substances with weight range from nanogram to pictogram can be sensed by means of the above-mentioned sensing methods or sensors.
The current nano-sized biosensors are mostly made of silicon nanowires or nanotubes.
As exemplified by the silicon nanowire, the surface of silicon is oxidized easily to form the native oxide layer. Accordingly, it is much easier to sense the presence of the electrified molecules such as proteins. However, it is not easy to manufacture the silicon nanowire, and the equipment required for manufacture is extremely expensive. O. Kuzmych et al., Nano technology 18, 375502 (2007) discloses a silicon nanowire sensor. The U.S. Pat. Nos. 7,129,554 and 6,870,235 both disclose a sensor that adopts silicon nanowire as field-effect transistor on which probe molecules are coupled for selective detection. By means of the structure of silicon nanowire, the above-mentioned sensors provide shorter sensing time while they still cause shortcomings including complexity or yield lower than 50% in manufacture.
As exemplified by the nanotube, it can be manufactured with high throughput, but it is not easy to obtain the nanotube with complete semiconductor properties by purification. In addition, it is very difficult to functionalize the nanotube for the researchers who have no chemistry background. The U.S. Pat. No. 7,318,908 discloses nanotube sensor arrays that adopt the nanotubes as field-effect transistors on which probe molecules are coupled for selective detection. However, the probe molecules are likely separated from the nanotubes according to the method disclosed in this reference. In addition, the Y. Chi et al. Science 293,1289 (2001) and N. W. S. Kam et al., J. Am. Chem. Soc. 126, 6850-6851 2004) also disclose nanotube sensors.
Star A et al., Proc. Natl acad. Sci. USA 103,921 (2006) discloses label-free detection of DNA hybridization using carbon nanotube network field-effect transistors. However, the use of specific fluorescent reading equipment is still unavoidable for reading fluorescent signals, causing complexity to detection procedure.
Accordingly, there still exists a need to develop a nanosensor capable of reading the molecular signals easily and improving the above-mentioned conventional problems.